Not Applicable
Not Applicable
This invention relates to adhesive articles with positionable and repositionable bonding properties, and more particularly to adhesive articles having a discontinuous layer of non-adhesive material applied onto a layer of adhesive material.
Traditional pressure sensitive adhesive (PSA) sheets, films, and tapes are sometimes difficult to apply because of the inherently tacky adhesive surface. Specifically, precise positioning of a tacky or xe2x80x9cquick stickxe2x80x9d adhesive product is difficult once adhesive contact has been made with a mounting surface, because it is difficult to slide or reposition the product. Also, air entrapment between the PSA article and mounting surface is a problem with dimensionally large PSA products. Additionally, xe2x80x9cblockingxe2x80x9d or adhesive-to-adhesive contact is problematic for dimensionally large products or thin gauge PSA products during pre-application handling.
The term xe2x80x9cpositionablexe2x80x9d is used herein to indicate a PSA article with a sufficiently low degree of tack (or no tack) to allow the adhesive surface to be slid across the mounting surface without sticking or grabbing. The term xe2x80x9crepositionablexe2x80x9d is used herein to indicate a PSA article that can be engaged with pressure to the mounting or application surface in a final manner, then removed therefrom, and then reapplied without significant degradation of positionable feature.
In some instances consumers may desire special PSA functional properties. For example, when using a PSA sheet, film, or tape as a protective covering, a consumer may want to selectively xe2x80x9cactivatexe2x80x9d only certain areas of the adhesive surface with pressure (i.e., just the edges of the PSA product) rather than across the entire adhesive surface of the PSA product. This feature would be applicable for wrapping or sealing applications. Additionally, consumers often desire a repositionability feature, allowing the product to be used a number of times while retaining the initial low-tack or no-tack properties.
Several methods and configurations have been developed to make application of PSA films and tapes easier. Frequently, application aids such as detergent and water have been used to reduce initial tack and impart positionable features in a typically non-positionable PSA product. Formulations vary, but typically include water, a surfactant or lubricant, and/or a solvent (generally an alcohol) that speeds bond formation and drying. The liquids tend to form a film between the adhesive and substrate, thus preventing contact and preadhesion. Unfortunately, the liquid is difficult to remove and is seldom completely removed. Additionally, most application aids affect the adhesive properties and prevent rapid formation of a strong bond between adhesive and substrate. The application aids may also mar or stain the mounting surface.
Some methods involve PSA products with reduced initial contact tack, but with more permanent long-term bonding. U.S. Pat. No. 5,346,766 discloses a positionable and repositionable PSA product which has an initially non-tacky surface. These characteristics are achieved by intimately mixing a detackifying resin and detackifying particulate into the adhesive film layer. After application, adhesion does build with passage of time or from heating. However, a product that provides a rapid increase in tack and adhesion properties is often more desirable to reduce installation time. Additionally, this product has a relatively narrow range of application temperatures.
Alternatively, discontinuous coatings of non-tack or low-tack materials projecting from the adhesive surfaces have been used to prevent premature contact (i.e., adhesion before it is wanted or expected) between the adhesive and substrate. The height of these discontinuous coatings or materials creates an air gap between the adhesive layer and the substrate. At the time of application, pressure is applied to initiate adhesion. There are several variations of this general technique described in the art.
U.S. Pat. No. 4,054,697 discloses deformable particles that recover their original shape after pressure is removed. However, U.S. Pat. No. 4,054,697 points out that with resilient particles, a sufficiently strong bond must be formed to the support surface to xe2x80x9cprevent the deformed particles from recovering to their undeformed dimensions,xe2x80x9d which xe2x80x9cwould cause the sheet material to come away from the support surfacexe2x80x9d. U.S. Pat. No. 4,054,697 further points out that xe2x80x9cit may be desirable for the pressure sensitive adhesive to be curable after the sheet material has been adheredxe2x80x9d to xe2x80x9covercome any tendency of the deformed particles to recover.xe2x80x9d
U.S. Pat. Nos. 3,331,729; 3,314,838; and 6,020,062 disclose using glass microspheres, micro-particles, or micro-balloons which are either partially or fully embedded in the adhesive layer. In these constructions, application pressure to the adhesive article crushes and/or embeds the microspheres into the adhesive layer. Crushing and/or embedding the microspheres into the adhesive layer permits the bulk of the adhesive to contact the mounting surface and instantly form a strong bond. Unfortunately, the destructive nature of the application process hinders re-use or repositioning of the product.
U.S. Pat. Nos. 4,376,151; 4,556,595; and 5,008,139 disclose non-adhesive solid particles, hollow particles, powders, or talcs which are either applied on the surface of the adhesive or embedded partially in the adhesive. Once a threshold application pressure is applied, the non-adhesive solids migrate into the adhesive layer and surface adhesion increases. Again, once the solids have migrated into the adhesive layer, such products lose the repositionable features.
Alternatively, discontinuous coatings of non-tacky materials that project from a relatively planar adhesive surface have also been used to prevent preadhesion of a PSA layer during application. These adhesive films and tapes have no adhesion when placed lightly against the mounting surface. Such films are disclosed in U.S. Pat. Nos. 3,554,835; 4,023,570; 4,054,697; 4,151,319; 5,008,139; and U.K. Patent No. 1,541,311. Manufacturing methods described in these references are often somewhat complex, involving the use of relatively expensive embossed release liners or multiple drying steps.
U.S. Pat. No. 5,591,290 discloses modifying the adhesive properties of a pre-manufactured laminate or label stock by applying a discontinuous layer of non-adhesive material to the PSA article. This process involves stripping a liner off a pre-manufactured adhesive laminate, applying a non-adhesive coating, and then re-laminating the liner. Although this method may be effective for small volume production, it is costly to add this additional manufacturing step. Additionally, with this manufacturing method it is difficult to control the three dimensional shape of the non-adhesive.
Other methods for handling preadhesion include formation of brittle plastic projections on a PSA article surface, such as disclosed in U.S. Pat. No. 3,301,741, or formation of small discrete clusters of particles protruding from the adhesive surface, such as disclosed in U.S. Pat. No. 5,141,790. For example in U.S. Pat. No. 5,141,790, the particles are tacky adhesive microspheres that provided weak bonding to a substrate when applied using light application pressure and strong bonding when applied using higher application pressures. However, this multi-adhesive construction tends to be more difficult to construct and adhesive particle transfer can be a problem.
In addition, U.S. Pat. Nos. 3,691,140 and 4,166,152 disclose microsphere and patterned adhesives exhibiting repositionable properties, and U.S. Pat. No. 4,735,837 discloses deformable microspheres which provide a rough or pebble-like surface and repositionable bond. In all these cases, the adhesive films readily form weak, repositionable bonds to a substrate, but do not form a strong, permanent bond.
U.S. Pat. No. 5,296,277 discloses an adhesive sheet having a microstructure adhesive surface comprising a uniform distribution of adhesive or composite adhesive xe2x80x9cpegsxe2x80x9d over the functional portion of an adhesive surface. The pegs protrude outwardly from the adhesive surface, and provide a sheet that is both positionable and repositionable when it is laid on a mounting surface. Pressing the adhesive surface against the mounting surface results in an instant formation of a strong bond between the adhesive sheet and the mounting surface. Such an adhesive also required a relatively expensive coincident microstructure release liner to protect the adhesive pegs during storage and processing.
Finally, U.S. Pat. No. 5,795,636 discloses another method of making a PSA article which includes forming a topologically microstructured adhesive surface. The surface is manufactured by casting the resin to a relatively expensive embossed release liner.
As discussed above, all of the disclosed methods have disadvantages. Accordingly, a need exists for an improved PSA article, and an economical method of making a PSA article having positionable and repositionable properties.
The present invention provides a pressure sensitive adhesive article, and a method of making the article. The method includes depositing a layer of liquid adhesive material onto a substrate, and depositing a layer of non-adhesive liquid material onto the liquid adhesive material, wherein the non-adhesive liquid material covers only a portion of the liquid adhesive layer. The liquid layers can be cured which allows winding the article onto a spool.
In another aspect of the invention the pressure sensitive adhesive article includes a substrate with a liquid adhesive layer deposited onto the substrate. At least one liquid non-adhesive structure is deposited onto a portion of the liquid adhesive layer, and the structure has a theoretical angle of contact with the adhesive layer which is greater than 0xc2x0.
A general objective of the present invention is to provide a pressure sensitive article which is positionable and repositionable. This objective is accomplished by providing an article having at least one non-adhesive structure covering a portion of a layer of an adhesive material to prevent the adhesive material from contacting a surface until desired.
Another objective of the present invention is to provide an economical method of making a pressure sensitive adhesive article. This objective is accomplished by providing a method which allows a user to control the geometry of non-adhesive structures on the surface of a layer of adhesive material.
The foregoing and other objectives and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention.